Switch mechanism



. March 10, 1942. G. CURRIE SWITCH MECHANISM Filed Jan. 29, 1941 INVENTOR Gi/ber'z (Jar-r26.

WITNESSES:

Patented Mar. 10, 1942 "r (caries SWITCH MECHANISM Gilbert Currie, Forest Hills, Pa., assignor to Westinghouse Electric & Manufacturing'Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 29, 1941, Serial No. 376,413

7 Claims.

My invention relates, generally, to switch mechanisms and, more particularly, to a quick make and break mechanism of the type described in Patent No. 1,606,801, issued November 16, 1926, to H. K. Krantz and assigned to the Westinghouse Electric & Manufacturing Company.

An object of my invention, generally stated, is to improve the switch mechanism disclosed in the aforesaid patent to Krantz.

A more specific object of my invention is to provide a quick-make-and-break switch mechanism in which the contact members are latched in either the closed or the open position.

A further object of my invention is to provide a quick-make-and-break operating mechanism which may be used with a switch of any type.

Other objects of my invention will be explained fully hereinafter'or will be apparent to those skilled in the art.

In accordance with my invention, the floating member or cam plate of an operating mechanism of the type described in the aforesaid patent is provided with a pair of notches or recesses for the crank pins which operate the contact members. The notches prevent creeping of the contact members until the cam plate passes over the mid or trip position. Thus, in switches having butt contact members full contact pressure is maintained up to the point of quick break.

Fora fuller understanding of the nature and objects of my invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a view partially in elevation and partially in section of a portion of the mechanism and the operating handle of a quick-makeand-break mechanism embodying my invention, the mechanism being shown in a position corresponding to the closed position of the contact members of the switch;

Fig. 2 is a View, similar to Fig. 1, showing the mechanism in a position corresponding to the open position of the contact members, and

Fig. 3 is a view similar to Fig. 1, showing a quick-make-and-break, mechanism constructed in the manner described in the aforesaid patent to Krantz.

Referring to the drawing and particularly to Fig. 3, the switch operating mechanism shown therein comprises a rotatable crank member 20 upon which a rotatable operating handle 2| is mounted for relative rotary movement therewith. The crank rod 20 is utilized for actuating the contact members of an enclosed switch structure (not shown). A crank member or plate 22 is fixed upon the crank rod 2!] and is pro- Vided with crank pins 23 and 24. Rotary movement of the plate 22 is limited by a stop pin 25 that is secured to the side wall of the housingfor the switch structure. An anti-friction roller 23 is provided on the pin 25. Movement of the crank rod 20 in either direction is limited by reason of the engagement of the plate 22 with the pin Etat the depressions 27 and 28 in the plate 22.

A floating member 29, hereinafter referred to as a cam plate, that is provided with an opening 3!}, is mounted upon the crank rod 29. The cam plate 29 is provided with a pair of angularly disposed arcuate slots 32' and 33, through which the stop pin 25 and the crank pins 23 and 24 extend.

As shown, the handle 2i is so shaped that it will engage the cam plate 29 at the point 34' when the handle is rotated in a counterclockwise direction and at the point 35 when it is rotated in a clockwise direction, thereby assisting a spring 38 which connects the cam plate 29 to the handle 2| in the operation of the switch contact members in the manner hereinafter described. The spring .38 yieldingly retains the cam plate 29 in the positions indicated in the drawing and is secured at one end to a lug 39 on the handle 2| (see Figs. 1 and 2) and at the other end to the cam plate 29 by means of the hook portion ll that extends through a notch 42 which is a continuation of the slots 32 and 33. The inner edges of the slots 32 and 33 constitute a pair of angularly disposed arcuate cam surfaces 43 and 44, respectively, the purpose of which will hereinafter appear.

Since the operation of the mechanism is fully described in the aforesaid patent to Krantz, it is believed to be unnecessary to describe the operation in detail in the present application. Briefly, the operation of the switch mechanism is as follows. Assuming that the parts of the switch operating mechanism are in the position shown in Fig. 3, wherein the switch is in its closed position, the operating handle 2! is rotated in a counterclockwise direction to open the switch. This movement of the operating handle causes the side of the handle to engage the cam plate 29 at the point 3 The natural tendency of the plate 29 would then be to rotate about the crank rod 20 as an axis of rotation, but such movement is prevented by reason of the engagement of the pin 25 with the cam tion 45, which will hereinafter be termed the clearance point of the cam surfaces 44 and 43, has passed the center of the stop pin 25.

7 24. The right-hand cam surface 43 is described When the clearance point 45 has passed the center of the stop pin 25, the spring 38' which has been extended during the opening movement of the operating handle, will suddenly contract and the end 46 of the slot 32 will engage the crank pin 23 and cause opening movement of the switch with a snap action. The crank plate 22, the operating handle 2! and the cam plate 29 will then occupy the same relative positions as is shown in Fig. 2, but the operating handle will, of course, be in the open position and the stop pin 25 will then be in the arcuate slot 32.

When the operating handleisrotatedinaclockwise direction to close the switch, the side wall of the handle engages the cam plate 29 at the point thereby causing the cam plate to rotate about the crank pin 24 as an axis of rotation until the clearance point 45 of the cam surfaces 43 and 44 again passes the center of the stop pin 25, at which time spring 38 will again contract and draw the end 41 of the arcuate slot 33 into engagement with the crank pin 24 and cause the crank plate 22 and the switch connected thereto to be moved to closed position with a snap action.

From the foregoing description, it is apparent that in switches of the knife blade type, in which this mechanism has been previously utilized, there is no force in the switch parts themselves which would tend to move the switch from either the on or the off position. In fact, in the on position, the friction between the blade and the jaws acts to resist the movement of the switch from the on position. However, if this mechanism is applied to a switch of the butt contact type in which the contact pressure applied to the springs exerts a constant force tending to open the switch, it will be evident from the foregoing explanation that the cam, as shown in Fig. 3, will not prevent premature movement or creeping of the contacts before the tripping point. In other words, a quick break will only apply to that part of the contact travel remaining when the point of the cam passes over the center line of the stationary roller, the actual break or separation of the contacts being made slowly.

Referring to Fig. 3, if an arc (xi-a be described with the center of the shaft 20 as center and touching the crank pin 23, it will be seen that it intersects the cam surface 43 at an acute angle. As the cam is moved to the tripped position in the manner hereinafter described, this angle becomes more acute and, as a result, the contact pressure will actually rotate the shaft 20, since the path of travel of the crank member pin 23 is along the arc a-a. On account of the manufacturing clearances between the crank member pin and the cam surface and because the radius of the crank pin is short in comparison with the lever arm of the contact, this premature movement of the switch will be sufficient to open the contacts before the point of the cam has passed over the center line of the stationary pin 25.

with the same radius R, but from a point to the right of the center of the crank pin 24 by a distance of approximately one-fourth of the crank pin diameter. Furthermore, recesses 48 and 49 are provided at the lower ends of the cam surfaces 43 and 44, respectively, by describing cam surfaces from these same centers with a radius equal to the radius of the crank .pin. The stationary pin 25 is located with the roller 28 just touching the cam surface.

In the position shown in Fig. 1, it is apparent that the cam 29 acted upon by the spring 38 and pivoting about the point where it touches the roller 26 tends to press the recess 48 in the lower part of the right-hand cam surface 43 against the right-hand crank pin 23. It is also apparent that the pin firmly held in the recess is prevented from moving by the sides of the recess 48.

As the cam is rotated to the left by the handle and up until the point where the cam passes over the clearance point 45, the notch still remains firmly pressed against the crank member pin and no movement of the crank pin is possible. It should b noted here that in order not to detract from the force holding the notch against the pin the force which moves the cam should be applied at a point such as to increase the pressure between the recess 48 and the pin 23.

When the cam snaps over to the off position,

as shown in Fig. 2, the spring pull exerts a force tending to move the cam to the left and forcing the notch 49 at the lower end of the left-hand cam surface 44 into engagement with the lefthand crank pin 24. Accordingly, as the cam is rotated to the right by the handle in the manner hereinbefore described, the notch 49 remains firmly pressed against the crank pin and no movement of the crank pin takes place until the cam passes the clearance point 45.

Summarizing, the improved cam structure herein disclosed provides a quick-make-and-break operating mechanism which maybe used on a switch of any type and in which the contact pressure in switches having butting contacts is maintained at full value up to the point of quick break.

Since numerous changes may be made on the above-described construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. Switch mechanism comprising a rotatable crank arm having an operating pin therefor, a fixed pin, a rotatable operating member, a floating cam member having a lost-motion connection to the operating member and provided with two angularly disposed cam surfaces one of which engages the fixed pin and the other of which engages the operating pin, one of said cam surfaces having a recess therein for receiving said operating pin, and a spring connecting said operating member and said floating cam, said fixed pin being disposed between said operating pin and the point of engagement between the operating member and the floating cam.

2. Switch mechanism comprising a rotatable crank arm having an operating pin therefor, a fixed pin, a rotatable operating member, a floating cam member having a lost-motion connection to the operating member and provided with two angularly disposed cam surfaces one of which engages the fixed pin and the other of which engages the operating pin, one of said cam surfaces having a recess at one end thereof for receiving said operating pin, and a spring connecting said operating member and said floating cam, said fixed pin being disposed between said operating pin and the point of engagement between the operating member and the floating cam.

3. Switch mechanism comprising a rotatable crank arm having a pair of operating pins therefor, a fixed pin, a rotatable operating member, a floating cam member having two angularly disposed cam surfaces one of which engages the fixed pin and the other of which engages one of said operating pins, said operating member being disposed to engage said cam at a predetermined point, said cam surfaces having recesses therein for receiving said operating pins, and a spring connecting said operating member and said floating cam, said fixed pin being disposed between said operating pins and the point of engagement between the operating member and the floating cam.

4. Switch mechanism comprising a rotatable crank arm having a pair of operating pins therefor, a fixed pin, a rotatable operating member, a floating cam member having two angularly disposed cam surfaces one of which engages the fixed pin and the other of which engages one of said operating pins, said operating member being disposed to engage said cam at a predetermined point, each of said cam surfaces having a recess at one end thereof for receiving one of said operating pins, and a spring connecting said operating member and said floating cam, said fixed pin being disposed between said operating pins and the point of engagement between the operating member and the floating cam.

5. Switch mechanism comprising a rotatable crank arm having a pair of operating pins therefor, a fixed pin, a rotatable operating member, a floating cam member having two angularly disposed cam surfaces for alternately engaging said fixed pin, each of said cam surfaces having a recess at one end thereof for receiving one of said operating pins, said operating member being disposed to engage said cam at a predetermined point, and a spring connecting said operating member and said floating cam to force said operating pins into said recesses alternately, said fixed pin being disposed between said operating pins and the point of engagement between the operating member and the floating cam.

6. Switch mechanism comprising a rotatable crank arm having a pair of operating pins therefor, a fixed pin, a rotatable operating member, a floating cam member having two angularly disposed cam surfaces for alternately engaging said fixed pin, each of said cam surfaces having a recess at one end thereof for receiving one of said operating pins, said operating member being disposed to engage said cam at a predetermined point, and a spring connecting said operating member and said floating cam to force an operating pin into the recess in whichever cam surface is not engaging said fixed pin, said fixed pin being disposed between said operating pins and the point of engagement between the operating member and the floating cam.

7. Switch mechanism comprising a rotatable crank arm having a pair of cylindrical operating pins therefor, a fixed pin, a rotatable operating member, a floating cam member having two angularly disposed cam surfaces for alternately engaging said fixed pin, each of said cam surfaces having an arcuate recess at one end thereof for receiving one of said operating pins, the radius of said recesses being substantially the same as the radius of said operating pins, said operating member being disposed to engage said cam at a predetermined point, and a spring connecting said operating member and said floating cam to force said operating pins into said recesses a1- ternately, said fixed pin being disposed between said operating pins and the point of engagement between the operating member and the floating cam.

GILBERT CURRIE. 

